Refactoring the network | Network World


The fundamental shift of the enterprise toward the cloud has posed a conundrum for many. The largest issue is the state of most enterprise networks. These networks were designed for an era gone by. Their original designs could not foresee the coming of technologies such as SDN, SDWAN, Segment Routing, the Cloud and an exponential increase in bandwidth that have all happened over the past 10 years.

The IPv4 Internet BGP routing table alone has experienced a 10% year over year growth between 2009 and 2017 along. In 2009 the table eclipsed 286,000 routes. Here in 2017 we are at approximately 650,000. These figures only account for IPv4 routes, and not the full IPv4 and IPv6 tables. During that same period we have gone from token ring and 10Base-T to 100GbE.

Many enterprises find that when they start down the Dev/Ops or Cloud path that their existing network is ill equipped to handle the loads and provide the stability and resilience that is needed.  Building a network is much like building a house. You must start with a good solid foundation. That foundation is the first three layers of the OSI model.

At layer one you need a good physical infrastructure and cabling plant, whether that be fiber optic, or copper twisted pair. Properly sized links are required to ensure adequate bandwidth to the applications which they carry. The second layer is a good switching infrastructure that has designated root bridges. These root bridges need to be aligned with the placement of the layer 3 gateways to ensure optimal traffic paths throughout the network. At layer 3 you need a good solid routing infrastructure that is functioning fully on a dynamic routing protocol (my personal preference is EIGRP due to the ability to summarize addressing at the interface easily). EIGRP can be a mistake though if your implementation is multivendor. While EIGRP is no longer a proprietary Cisco protocol, no mainstream switch, route, or firewall vendors have implemented it into their equipment.

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